Helicobacter pylori infects more than half of the global population and causes gastric disorders. The increasing development of antibiotic resistance by the bacterium continues to limit treatment options. The identification and characterisation of novel therapeutic targets are necessary for successful future treatment of the infection. One potential target for therapeutic intervention is the gpt gene encoded by hp0735 (jhp0672) in H. pylori strain 26695 (J99). This gene produces a putative xanthine-guanine phosphoribosyltransferase (XGPRTase), an enzyme of the purine salvage synthesis pathway. This project employed theoretical, molecular and biochemical approaches to investigate features of H. pylori gpt and XGPRTase that will serve to ascertain their therapeutic potential. The production of a functional XGPRTase by H. pylori was investigated in cell-free extracts, and the kinetic parameters of this activity were compared to those of purified rXGPRTase enzyme. The three 6-oxopurine substrates were recognised by rXGPRTase and allosteric kinetics were observed for some substrates of the enzyme in cell-free extracts and for purified enzyme. These observations indicate complex regulation and an influence of cellular interactions on activity. Bioinformatics were employed to analyse XGPRTase phylogeny, and threading techniques used to build a structural model of XGPRTase. The enzyme is significantly divergent from the equivalent mammalian enzyme, and modelling identified specific features of the enzyme. Molecular approaches were utilised to analyse the essential role of gpt in H. pylori survival. These included insertional inactivation of the gpt in wild-type H. pylori strains and in mutants possessing a complementing copy of the gene present at the rdxA locus. No mutants were recovered with inactivated gpt possibly as a result of pleiotropic effects. Plasmid-mediated complementation was attempted employing IPTG-inducible shuttle vectors and did not yield any mutants. Further characterisation of H. pylori XGPRTase was performed by determining the effects of nucleotide monophosphates and purine analogues on enzyme activity. Inhibition by GMP was observed in all cases, however differences in the inhibition by other nucleotide monophosphates were found between cell-free extracts and the recombinant enzyme. Inhibition of rXGPRTase activity was observed by the purine analogue 6-mercaptopurine ribose, a compound that previously has been shown to inhibit H. pylori growth in culture.

Includes bibliographical references. / 59 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Various articles published by John Robin Warren on the discovery and pathology of Helicobacter pylori. / Thesis (M.D.)--University of Adelaide, Dept. of Medicine, 2000

Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7281. Adviser: Karen J. Goodman. Includes bibliographical references.

Darbo tikslas - įvertinti sergančiųjų funkcine dispepsija skrandžio gleivinės morfologinius pakitimus bei jų pokyčius gydant skirtingomis augalinės kilmės antioksidanto astaksantino dozėmis. Tikslui pasiekti buvo nustatyti ir išspręsti šie uždaviniai: įvertinti infekuotumą Helicobacter pylori mikroorganizmais bei skrandžio gleivinės histomorfologinius pakitimus pagal Sidnėjaus ir OLGA klasifikacijas sergantiesiems funkcine dispepsija; ištirti funkcine dispepsija sergančių ligonių uždegimo žymenų IL-4, IL-6, IL-8, IL-10, IFN-γ bei lastelių žymenų CD4, CD8, CD14, CD19, CD25, CD30 raišką skrandžio gleivinėje; palyginti funkcine dispepsija sergančių ligonių, gydytų augalinės kilmės antioksidanto astaksantino skirtingomis dozėmis ir placebu, skrandžio gleivinės morfologinius pokyčius; palyginti funkcine dispepsija sergančių ligonių, gydytų augalinės kilmės antioksidantu astaksantinu ir placebu, uždegimo žymenų IL-4, IL-6, IL-8, IL-10, IFN-γ bei lastelių žymenų CD4, CD8, CD14, CD19, CD25, CD30 raišką skrandžio gleivinėje. / The aim of the study was to evaluate histomorphological changes of the gastric mucosa in functional dyspepsia patients and their dynamics after treatment with the natural antioxidant astaxanthin. The following objectives were established and reached: to determine the presence of Helicobacter pylori infection and evaluate the histomorphological changes of gastric mucosa in functional dyspepsia patients; to evaluate interleukins IL-4, IL-6, IL-8, IL-10 and interferon-γ as well as the cell markers CD4, CD8, CD14, CD19, CD25 and CD30 in functional dyspepsia patients; to evaluate histomorphological changes of the gastric mucosa in functional dyspepsia patients after treatment with the natural antioxidant astaxanthin; to evaluate interleukins IL-4, IL-6, IL-8, IL-10 and interferon-γ as well as the cell markers CD4, CD8, CD14, CD19, CD25 and CD30 in functional dyspepsia patients and their dynamics after treatment with the natural antioxidant astaxanthin.

Helicobacter pylori infects more than half of the global population and causes gastric disorders. The increasing development of antibiotic resistance by the bacterium continues to limit treatment options. The identification and characterisation of novel therapeutic targets are necessary for successful future treatment of the infection. One potential target for therapeutic intervention is the gpt gene encoded by hp0735 (jhp0672) in H. pylori strain 26695 (J99). This gene produces a putative xanthine-guanine phosphoribosyltransferase (XGPRTase), an enzyme of the purine salvage synthesis pathway. This project employed theoretical, molecular and biochemical approaches to investigate features of H. pylori gpt and XGPRTase that will serve to ascertain their therapeutic potential. The production of a functional XGPRTase by H. pylori was investigated in cell-free extracts, and the kinetic parameters of this activity were compared to those of purified rXGPRTase enzyme. The three 6-oxopurine substrates were recognised by rXGPRTase and allosteric kinetics were observed for some substrates of the enzyme in cell-free extracts and for purified enzyme. These observations indicate complex regulation and an influence of cellular interactions on activity. Bioinformatics were employed to analyse XGPRTase phylogeny, and threading techniques used to build a structural model of XGPRTase. The enzyme is significantly divergent from the equivalent mammalian enzyme, and modelling identified specific features of the enzyme. Molecular approaches were utilised to analyse the essential role of gpt in H. pylori survival. These included insertional inactivation of the gpt in wild-type H. pylori strains and in mutants possessing a complementing copy of the gene present at the rdxA locus. No mutants were recovered with inactivated gpt possibly as a result of pleiotropic effects. Plasmid-mediated complementation was attempted employing IPTG-inducible shuttle vectors and did not yield any mutants. Further characterisation of H. pylori XGPRTase was performed by determining the effects of nucleotide monophosphates and purine analogues on enzyme activity. Inhibition by GMP was observed in all cases, however differences in the inhibition by other nucleotide monophosphates were found between cell-free extracts and the recombinant enzyme. Inhibition of rXGPRTase activity was observed by the purine analogue 6-mercaptopurine ribose, a compound that previously has been shown to inhibit H. pylori growth in culture.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Thesis (M.D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 195-247).

Thesis (M.D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 195-247) Also available in print.

Introdução: A infecção por Helicobacter pylori (H. pylori) tem distribuição geográfica universal, porém apresenta grande variabilidade na prevalência, nos fatores de virulência e na apresentação clínica de acordo com a população estudada. No Brasil, um país continental composto por etnias e hábitos culturais diversos, o comportamento da infecção também parece variar conforme já demonstrado em diferentes estudos. O presente estudo foi realizado com o objetivo de descrever a prevalência da infecção por cepas de H. pylori cagA-positivo em um grupo de crianças e adolescentes submetidos a esofagogastroduodenoscopia (EGD) em Porto Alegre, cidade situada na região Sul do Brasil. Materiais e Método: Noventa e oito fragmentos de biópsia gástrica de crianças e adolescentes foram submetidos à pesquisa de cepas de H. pylori cagA-positivo pelo método da reação em cadeia da polimerase (PCR). Resultados: A prevalência de cepas de H. pylori cagA-positivo foi de 29,6% (IC95% 18 a 43,6%). Não foram encontradas diferenças estatisticamente significativas quanto às características clínicas, demográficas, endoscópicas e histológicas dos pacientes infectados por cepas cagA-positivo em relação aos infectados por cepas cagA-negativo. Conclusões: O estudo demonstrou uma baixa prevalência da infecção por cepas de H. pylori cagA-positivo em crianças e adolescentes submetidos à EGD no sul do Brasil em comparação a estudos realizados com crianças de outras regiões do Brasil. Não houve associação entre a presença de cepas cagA-positivo e apresentação clínica adversa na amostra estudada. / Introdution: Helicobacter pylori (H. pylori) has a worldwide distribution, but the prevalence of infection, virulence factors, and clinical presentation vary widely according to the studied population. In Brazil, a continental country composed of several ethnicities and cultural habits, the behavior of infection also appears to vary, as many other studies have shown. Objective: The present study aimed to describe the prevalence of infection with cagApositive H. pylori strains in a group of children and adolescents who underwent esophagogastroduodenoscopy (EGD) in Porto Alegre, a city in Southern Brazil. Methods: Ninety-eight gastric biopsy specimens of children and adolescents were tested for presence of H. pylori cagA-positive strains by the polymerase chain reaction (PCR) method. Results: The prevalence of H. pylori cagA-positive strains was 29.6% (IC95% from 18 to 43.6%). There were no statistically significant differences in clinical or demographic characteristics or in the endoscopic and histological features of patients infected with cagA-positive strains as compared with those infected by cagA-negative strains. Conclusions: The study showed a low prevalence of infection with cagA-positive H. pylori strains among children and adolescents who underwent EGD in southern Brazil, in comparison to studies conducted with children from other regions of Brazil. There was no association between the presence of cagA-positive strains and more severe clinical presentations in the studied sample.